( 50 ) 



arriving at a scientific result was to take parts of sick })laiits to the 

 laboratory and to study them there. 



Meanwhile a continued walk through the tobaccofields had revealed 

 that this was a case not of a bacterial disease as had originally been 

 supposed but of a sclerotial disease, since in various places in a 

 greater or less degree spots were found on leaves and stems consisting 

 of a white down and besides greater or smaller black grains, embedded 

 in or lying on that down, so that on account of other observations 

 made elsewhere, it seemed |)rol)able that these black organisms under 

 favourable conditions might ju-oduce an ascigerous generation, from 

 tiie morphological properties of which the place of the fungus in the 

 system and its identity or difference ^^ ith otiier kno\vn species niiglit 

 be inferred. 



The richest crop of material tor experiments Avas gathered in the 

 dampest ])laces, i.e. in the corners of hedges of scarlet-runners, ^vhile 

 on the other hand in iho \icinity of French beans often not a single 

 grain was to be fouml. Where flowers or fh^wer-clusters of scarlet- 

 runners were held fast in the axils of tobaccoleaves, sclerotia were 

 rarely sought in vain. It can be understood that the uninitiated — 

 growers and working-men — imagined that the source of the evil 

 had entirely to be sought in the blossoms of' the scarlet-runners. 



II. Investigation of the disease which had attacked the plants. 



On various days of September 1902 sick parts of stems and leaves 

 were taken home from the tobaccofields as well as from the drying 

 sheds. In doing so each leaf and each stem were separately put into 

 a sterilised tube and in the laboratory placed into a sterilised glass- 

 box over wet fütering paper. 



At a temperature of 22° (J. a distinct change could already he 

 observed in all the objects after 24 hours. They had developed a 

 flimsy, transparent, much-branched mycelium. At a lower temperature 

 the same phenomenon had occurred though less vigorously. 



After 3 X 2'^ hours small bits of the ol)tained net of tiu*eads were 

 with the necessary precautions placed on malt-gelatine and kept at 

 22°. Already after 24 hours these bits had grown much and it was 

 possible after another 24 hours to take away new bits from the 

 margin of the circular cultures which had now grown to a diameter 

 of 3,5 centimeters and to inoculate them on freshly prepared malt- 

 gelatine. In this way a sufficient quantity of pure cultures were 

 obtained in a relatively short time. 



As healthy tobacco-plants were largely at our disposal, it was 



